Optical pickup

摘要

There is provided an optical pickup which comprises a light source, an objective lens for converging a beam from the light source onto an optical disc, a diffraction grating for passing a beam returning from the optical disc, a photo-detector for receiving returning beams passing through the diffraction grating. The diffraction grating is divided into two areas, each area including alternatively arranged first diffraction grating pattern and second diffraction grating pattern.